Project Summary Our proposal seeks to build upon the success of our lab investigating the electrophysiology of human memory through novel experiments that will elucidate hippocampal?parietal interactions in memory processing. The key innovations of this proposal are the application of direct brain stimulation to the mesial parietal cortex and the adaptation of an associative recognition paradigm to intracranial data. We will take advantage of our high-volume epilepsy surgical center specializing in stereo EEG electrode implantation. In our first aim, we will compare how electrophysiological patterns of brain activation differ between free recall (which comprises the bulk of intracranial memory data) and associative recognition, specifically examining properties of theta oscillations in the anterior versus posterior hippocampus. In the second aim, we will apply deep brain stimulation to the mesial parietal cortex during memory encoding and retrieval, observing differences in memory performance and hippocampal oscillatory activity that will inform hypotheses of how this area supports episodic memory. In Aim 3, we will use machine learning classifiers to understand how mesial parietal stimulation affects memory performance via its impact on brain oscillatory activity in a responsive stimulation paradigm. These experiments will utilize our lab?s knowledge and infrastructure gained through participation in the DARPA Restoring Active Memory project. While our proposal is highly innovative, our center?s proven success in recruiting a large volume of stereo EEG patients for memory research, data collection, and the application of advanced analytic techniques give us confidence that we will collect high quality data addressing the critical gaps in the understanding of human memory.